In U.S. application Ser. No. 787,983, filed Apr. 15, 1977 by Richard P. Goldhaber, a method and apparatus for determining ultrafiltration during dialysis is shown. Basically, a membrane dialyzer unit is placed on a mounting in dialysis apparatus. The mounting comprises a horizontal sliding valve connected to the inlet and the outlet of the dialyzer. Accordingly, by sliding the dialyzer and the valve into one valving position, the dialysis solution passes through the valve into the inlet and out of the outlet of the dialyzer. When the dialysis unit and the sliding valve are moved in the other horizontal sliding position, both the inlet and the outlet of the dialyzer unit are sealed. Since blood can still pass through the dialysis unit, ultrafiltration still takes place causing liquid to rise in a reservoir communicating with the sealed portion of the dialysis solution flow path, to measure ultrafiltration.
However, in practical use, certain disadvantages of construction have been found in this apparatus. For example, the horizontal sliding valve of the Goldhaber application comprises first and second sliding members positioned against each other in sliding relation, specifically to pivot back and forth into the open and closed valving positions. This valve has been found to be particularly difficult to seal, since the O-rings surrounding the respective valve orifices tend to be moved out of position, since the sliding valve members pivot in a plane which is parallel to the plane of the sealing O-rings. It has been found that in order to obtain effective sealing, the pressure between the two valve members must be so great as to run a risk of dislodging the O-ring, or not being able to slide the valve at all, and causing undue wear as the dialysis unit valve member is operated.
In accordance with this invention, an ultrafiltration monitoring device for use in a dialyzer is provided which exhibits more reliable long-term operation, since the O-rings are positioned so that the direction of sliding valving motion in the apparatus of this invention is perpendicular to the plane of the O-ring rather than parallel thereto as in the previous application. Accordingly, better sealing and more reliable sealing for a longer period of time is provided.
Also, the ultrafiltration testing device of this invention utilizes a novel, longitudinally movable and clampable retention member for bearing against the top of and holding a dialyzer member within the device of this invention.